The invention relates to a signal amplitude limiting circuit and a filter circuit that are for instance suitable for circuit-integration.
One conventional filter circuit using transconductance amplifier is disclosed in Japanese Patent Publication No. 11-004139.
The above filter circuit is composed of a transconductance amplifier and a capacitor. The transconductance amplifier (which is referred to as a voltage control current source in the above-described official gazette) is replaced with the inductor and resistance portions in a double terminated LC ladder filter circuit. The characteristic of the filter circuit is maintained by adjusting a transconductance (gm) of the transconductance amplifier in response to a variation due to the temperature and an irregularity of element values occurred during circuit-integration.
However, the above-described conventional filter circuit has a transconductance amplifier connected directly to an input terminal, so that it has the problem that the operations of the filter circuit might not be carried out or may become unstable when an input signal to the filter circuit has a voltage amplitude that exceeds the input dynamic range of the transconductance amplifier.
On account of this, there is required a filter circuit with a transconductance amplifier which be relied upon to provide stable operation even when an input signal has a large voltage amplitude, and a signal amplitude limiting circuit suitable for the application to such filter circuit.